A multi-mutualist simulation: Applying biological market models to diverse mycorrhizal communities

We present a cellular automaton that simulates the interaction between a host tree and multiple potential mycorrhizal symbionts and generates testable hypotheses of how processes at the scale of individual root tips may explain mycorrhizal community composition. Existing theoretical biological market models imply that a single host is able to interact with and select from multiple symbionts to organize an optimal symbiont community. When evaluating the tree–symbiont interaction, two scales must be considered simultaneously: the scale of the entire host plant at which carbon utilization and nutrient demands operate, and the scale of the individual root tip, at which colonization and carbon-nutrient trade occurs. Three strategies that may be employed by the host tree for optimizing carbon use and nutrient acquisition through mycorrhizal symbiont communities are simulated: (1) carbon pool adjustment, in which the plant controls only the total amount of carbon to be distributed uniformly throughout the root system, (2) symbiont selection, wherein the plant opts either for or against the interaction at each fine root tip, and (3) selective carbon allocation, wherein the plant adjusts the amount of carbon allocated to each root tip based on the cost of nutrients. Strategies were tested over various nutrient availabilities (the amount of inorganically and organically bound nutrients). Success was defined on the basis of minimizing carbon expended for nutrient acquisition because this would allow more carbon to be utilized for growth and reproduction. In all cases, the symbiont selection and selective carbon allocation strategies were able to meet the nutritional requirements of the plant, but did not necessarily optimize carbon use. The carbon pool adjustment strategy is the only strategy that does not operate at the individual root tip scale, and the strategy was not successful when inorganic nutrients were scarce since there is no mechanism to exclude suboptimal symbionts. The combination of the symbiont selection strategy and the carbon pool adjustment resulted in optimal carbon use and nutrient acquisition under all environmental conditions but result in monospecific symbiont assemblages. On the other hand, the selective carbon allocation strategy is the only strategy that maintained successful, multi-symbiont communities. The simulations presented here thus imply clear hypotheses about the effect of nutrient availability on symbiont selection and mycorrhizal community richness and composition.     

Computer simulation applied to the biological control of the insect Aphis gossypii for the parasitoid Lysiphlebus testaceipes

In integrated pest management (IPM), biological control is one of the possible options for the prevention or remediation of an unacceptable pest activity or damage. The success of forecast models in IPM depends, among other factors, on the knowledge of temperature effect over pests and its natural enemies. In this work, we simulated the effects of parasitism of Lysiphlebus testaceipes (Cresson, 1880) (Hymenoptera: Aphidiidae) on Aphis gossypii (Glover, 1877) (Hemiptera: Aphididae), a pest that is associated to crops of great economic importance in several parts of the world. We made use of experimental data relative to the host and its parasitoid at different temperatures. Age structure was incorporated into the dynamics through the Penna model. The results obtained showed that simulation, as a forecast model, can be a useful tool for biological control programs.     

利福平废水处理的工艺实验研究

采用水解酸化-UASB(上流式厌氧污泥反应床)-接触氧化-生物活性炭工艺对利福平废水进行了生化处理。结果表明:水解酸化可以有效提高废水的可生化性,大幅度提高后续的厌氧-好氧处理效果,工艺末端的生物活性炭深度处理可以有效的去除好氧出水的COD和色度,使得出水达到GB8978-1996《污水综合排放标准》的规定标准。     

复合式接触氧化-过滤沉淀工艺处理医院污水

结合工程实例介绍了复合式接触氧化-过滤沉淀工艺在医院污水处理中的应用。对接触氧化进行了改进,把原有接触氧化池分成若干单元池,通过控制曝气量,营造好氧、缺氧环境,以完成脱碳和硝化反硝化脱氮过程,并辅以过滤沉淀技术。工程实践证明,用该工艺处理完全能够达到相关排放标准的要求,是一种适宜于医院污水处理的经济、高效的污水处理技术。     

二段生化+物化法处理污水及中水回用的研究与设计

本文采用二段生物处理和物化处理相结合的处理方法处理某大学校区生活污水,实现处理效率高、占地面积小、工程投资低等特点,处理后各项指标均达到《生活杂用水水质标准》（CJ25．189）,处理费用为0．690元／m^3。     

玻璃纤维负载P25光催化接触氧化活性艳红X-3B

在玻璃纤维上焙烧P25制备了负载型TiO2光催化剂,探讨了焙烧温度对催化活性的影响,设计了光催化接触氧化反应器,并以活性艳红X-3B为模型污染物,考察溶液pH值、共存阴离子(CO₃^2-、SO₄^2-、Cl-)对光催化反应的影响.结果表明,焙烧温度直接影响负载后催化剂的活性,300℃负载时活性最高,SEM照片显示此时P25与载体结合牢固、负载颗粒均匀.酸性条件对活性艳红X-3B的降解有利,当溶液初始pH由2.0上升到10.0时,活性艳红X-3B的降解率从90.06%下降至42.71%.共存的CO₃^2-、SO₄^2-对活性艳红X-3B降解的影响不大,但Cl^-对氧化过程有明显的抑制,使活性艳红X-3B的降解率下降17.03%.利用成熟的光催化剂P25,通过烧结的方法制备负载型催化剂是当前替代粉末催化剂的较为可行的方案.     

活性污泥法处理低浓度含磷废水的试验研究

对比研究了厌氧—好氧交替条件下(AAA工艺)活性污泥对三组磷浓度不同的模拟生活废水的除磷效果。试验结果表明,活性污泥对磷浓度为6mg/L左右的废水处理效果最好,磷去除率可达97%;对磷浓度为16.66mg/L和2mg/L左右废水的磷去除率则分别为78.4%和75.3%;并探讨了活性污泥法的除磷机理。     

Application of sediment quality guidelines in the assessment and management of contaminated surficial sediments in Port Jackson (Sydney Harbour), Australia

Sediments in the Port Jackson estuary are polluted by a wide range of toxicants and concentrations are among the highest reported for any major harbor in the world. Sediment quality guidelines (SQGs), developed by the National Oceanographic and Atmospheric Administration (NOAA) in the United States are used to estimate possible adverse biological effects of sedimentary contaminants in Port Jackson to benthic animals. The NOAA guidelines indicate that Pb, Zn, DDD, and DDE are the most likely contaminants to cause adverse biological effects in Port Jackson. On an individual chemical basis, the detrimental effects due to these toxicants may occur over extensive areas of the harbor, i.e., about 40%, 30%, 15% and 50%, respectively. The NOAA SQGs can also be used to estimate the probability of sediment toxicity for contaminant mixtures by determining the number of contaminants exceeding an upper guideline value (effects range medium, or ERM), which predicts probable adverse biological effects. The exceedence approach is used in the current study to estimate the probability of sediment toxicity and to prioritize the harbour in terms of possible adverse effects on sediment-dwelling animals. Approximately 1% of the harbor is mantled with sediment containing more than ten contaminants exceeding their respective ERM concentrations and, based on NOAA data, these sediments have an 80% probability of being toxic. Sediment with six to ten contaminants exceeding their respective ERM guidelines extend over approximately 4% of the harbor and have a 57% probability of toxicity. These areas are located in the landward reaches of embayments in the upper and central harbor in proximity to the most industrialised and urbanized part of the catchment. Sediment in a further 17% of the harbor has between one and five exceedences and has a 32% probability of being toxic. The application of SQGs developed by NOAA has not been tested outside North America, and the validity of using them in Port Jackson has yet to be demonstrated. The screening approach adopted here is to use SQGs to identify contaminants of concern and to determine areas of environmental risk. The practical application and management implications of the results of this investigation are discussed.     

AB—A／O组合工艺生物脱氮的试验研究

采用AB—A/O相结合的组合工艺,对城市生活污水和部分工业废水混合的污水进行实验室处理试验研究,其污水中的COD、BOD_5去除率>90％,TN去除率60％—80％,NH_3-N去除率>90％。试验结果表明,采取这一组合处理工艺,具有良好的生物脱氮能力。通过试验研究,在提出处理工艺参数的同时,还较深入地讨论了泥龄、硝化时间和反硝化时间、污泥产量、回流比、硝化速率和反硝化速率、C/N比、A段和B段的合理配合、碳和氮的转移等问题。     

Effects of Management on Understory Diversity in the Forest Ecosystems of Northern Spain

Pine plantations are an alternative to marginal agriculture in many countries, and are often presented as an option that improves biodiversity. However, these plantations can have adverse environmental effects if improperly managed. To evaluate the effect of forest management practices on biodiversity, the diversity, species richness, dominance and frequency of understory woody plant species in different forests of the Basque Country (northern Spain) were compared. Plantations of exotic conifers (Pinus radiata [D.] Don) of different ages were compared with deciduous forests of Quercus robur L. and Fagus sylvatica L. The effects of different types and intensities of management were taken into account. The differences observed were mainly conditioned by the intensity of forestry management, although the response varied according to forest type and age. In unmanaged pine plantations, the diversity and species richness of the understory increased rapidly after planting (while dominance decreased), remained stable in the intermediate age range, and reached a maximum in plantations more than 25 years of age. Management practices resulted in decreased understory diversity and species richness, as well as greater dominance. This was more pronounced in younger than in older stands. Moderate management, however, favored a greater diversity of the understory in deciduous forests. The species composition of the plantations and deciduous forests were different, the latter having a wider range of characteristic species. Knowledge of how forestry practices influence biodiversity (in terms of diversity, richness, dominance, and species composition) may allow predictions to be made about the diversity achievable with different management systems.